Use a script that clean a combined vector and image drawing imported from PDF's.
It's not possible to avoid that some layers and areas appear as black images.
Have used MRI to try to spot any differences, and almost all images to keep appear to use UINameSingular = 'Bitmap with transparency' and the rest use 'Bitmap'.
A few of those set to 'Bitmap' aren't black and should therefore be kept.
How can one sample and spot if an image is only black in OpenOffice basic?